In general, representative large-scale display apparatuses may include Liquid Crystal Displays (LCDs) and Plasma Display Panels (PDPs), for example.
Unlike self-emission type PDPs, LCDs essentially need a separate light unit due to absence of self light emitting devices.
Light units for use in LCDs are classified into edge type light units and vertical type light units according to positions of light sources. In an edge type light unit, light sources are arranged at left and right edges or upper and lower edges of an LCD panel and a light guide plate is provided to uniformly distribute light throughout a surface of the LCD panel, which ensures uniform luminance and enables production of an extremely thin display panel.
A vertical type light unit is normally applied to displays of 20 inches or more. The vertical type light unit advantageously has greater light efficiency than the edge type light unit owing to a plurality of light sources being arranged below a panel and thus, is mainly used in a large-scale display requiring high luminance.
Conventional edge type or vertical type light units have adopted Cold Cathode Fluorescent Lamps (CCFL) as a light source.
The light units using CCFLs, however, have several disadvantages, such as consumption of a great quantity of power because power should always be applied to a CCFL, low color reproduction efficiency of about 70% that of a Cathode Ray Tube (CRT), and environmental pollution due to use of mercury.
Currently, light units using Light Emitting Diodes (LEDs) are being studied as a solution to the above described problems.
In the case of light units using LEDs, turning on or off a part of an LED array is possible, which can achieve remarkable reduction in power consumption. In particular, RGB LEDs exhibit color reproduction beyond 100% of a color reproduction range proposed by the National Television System Committee (NTSC) and can provide more vivid images to consumers.